Unitized plate wire memory plane

ABSTRACT

Plated wires are incorporated as an integral part of a dielectric support medium, thereby forming a plated wire memory plane. The tensile strengths or thermal coefficients of expansion of the plated wires and the dielectric support medium are so related that over a desired operating temperature range the plated wires are maintained in a relatively stress-free condition.

United States Patent 1 McPherson [54] UNITIZED PLATE WIRE MEMORY PLANE[75] Inventor: Gary C. McPherson, Excelsior,

Minn. 1

[73] Assignee: Honeywell Inc., Minneapolis, Minn.

[22] Filed: April 19, 1971 [21] Appl.No.: 135,286

[52] US. CI..340/I74 PW, 340/174 TF, 340/174 JA,

511 1111. c1 ..Gllc5/04,Gl1c 11/14 58 Field of Search....340/l74 TF, 174PW; 29/604; 156/52, 179, 275, 309

[56] References Cited UNITED STATES PATENTS 3,083,353 3/1963 Bobeck..340/174 TW 3,553,648 1/1971 Gorman et al ..340/l74 PW OTHERPUBLICATIONS The Western Electric Engineer-Vol. 6, No. 3, July 1962 pg35-39. V 7

Primary Examiner-James W. Moffitt Att0mey-Lamont B. Koontz and Omund R.Dahle [57] ABSTRACT 18 Claims, 4 Drawing Figures ",l f/////////////7i/-///l EXTERNAL BIAS, 1 h 1 2.. Q- TENSION PATENTEDJM 9 I973 3,710,355

SHEET 1 [1F 2 "-E//////////////$ U//////fl EXTERNAL ems TENSIONLZ///////// /l/////////// I INVENTOR. GARY c. McPHERSON Y B 0mg 00%.

A TTOfP/VE X PAIENTEDJAH 91975 3.710.355

IN VEN TOR.

Fla 4 T 1/ BY GARY c. McPHERSON A TTOR/VEX UNITIZED PLATE WIRE MEMORYPLANE B ACKGROUND (IF THE INVENTION This invention relates, in general,to a memory device and in particular to a plated wire memory of unitizedconstruction. As used in this specification, the term plated wire refersto small diameter wires having a magnetic coating.

The conventional plated wire memory plane consists of a dielectricsupport medium having a plurality of parallel spaced holes, or tunnels.A plated wire having a diameter smaller than that of the tunnel ispositioned in each tunnel. A grid of substantially parallel conductorsis attached to the opposing surfaces of the dielectric support medium.The substantially parallel conductors are positioned orthogonal to theplated wires so as to form word straps.

The most widely used method of forming a tunnel structure has been toembed a plurality of parallel wires between two sheets of dielectricmaterial which are bonded together. The wires are then removed to formparallel holes within the laminate. The plated wires are threaded intothe tunnels after the structure is fabricated, and are free to slidewithin the tunnel in order to avoid subjecting the wires to physicalstress. The wires must be held in a stress-free condition because themagnetic properties of plated wires are strain sensitive.

As can be seen, it has not been possible to fabricate a plated wirememory device which is uniformly reproducible using low cost massproduction processes. Fabrication of a dielectric support medium havinga large number of small parallel tunnels has added to manufacturingcosts. The largest difficulty of the conventional plated wire memoryplane has been the requirement that each plated wire, which has adiameter of 5 mils or less, must be individually inserted by hand intothe tunnel structure. This difficult and expensive process greatlyincreases the cost of plated wire memory planes.

SUMMARY OF THE INVENTION The present invention provides a plated wirememory plane in which the plated wires are incor porated as an integralpart of the dielectric support medium. The thermal coefficients ofexpansion of the plated wires and the dielectric support medium are sorelated that over a desired operating temperature range the plated wiresare maintained in a relatively stressfree condition. In this manner, aplated wire memory plane is provided which is simple and economical tomanufacture using low cost mass production processes. The expensivetunnel structure type dielectric support medium is avoided and thedifficult and expensive process of inserting the plated wires in thetunnel structure is eliminated.

In one embodiment of the present invention the tensile strength of thematerial forming the sheet-like dielectric support medium is much lessthan the tensile strength of the material forming the plated wires. Theplated wires are arranged in a substantially parallel grid. Thedielectric support medium embeds each of the plated wires of the grid.The ratio of the cross-sectional areas of the dielectric support mediumand the grid is such that the total tensile strength of the crosssectionof the dielectric support medium is less than the total tensile strengthof the grid. Therefore, the dielectric support medium applies anegligible amount of stress to the plated wires over a desired operatingtemperature range.

In another embodiment of the present invention, a reinforced dielectricsupport medium having a tensile strength comparable to that of theplated wires is utilized. As in the first embodiment, the plated wiresare arranged in a substantially parallel grid. Each wire has a residualbias tension applied to it. The dielectric support medium has a thermalcoefficient of expansion which is different from the thermal coefficientof expansion of the plated wires. The dielectric support medium embedsand adheres to each of the plated wires and applies a compressive forceto the wires over a desired operating temperature range due to thedifference between the thermal coefficients of the plated wires and thedielectric support medium. The compressive force effectively cancels theresidual bias tension on the wires over the desired operatingtemperature range such that the plated wires are maintained in arelatively stress-free condition.

BRIEF DESCRIPTION OF THE DRAWING FIG. 4 shows a memory plane in which aportion of v the dielectric support medium has been removed to exposethe plated wire ends for electrical connection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a methodof fabrication of a unitized plated wire memory plane is shown. Aplurality of plated wires 10 are arranged in a substantially parallelgrid. To each wire is applied a constant external bias tension,illustrated by arrows in FIG. 1. The number of plated wires used isdependent upon the storage capacity desired for the memory device. Theplated wires are positioned between a first and a second sheet ofdielectric material 11 and 12, respectively. The dielectric material hasa tensile strength which is much less than the tensile strength ofplated wires 10. At the extreme top and bottom of the assembly are firstand second sheets of metal foil 13 and 14. Polished metal platens l5apply a pressure to the assembly sufficient to cause bonding. The resultis a unitary laminated structure.

FlG2 shows a section of the completed laminate and illustrates how thefirst and second sheets 11 and 12 have bonded together to permanentlyembed plated wires 10 in a unitary body of dielectric material hereafterreferred to as dielectric support medium 20. The dielectric material ofdielectric support'medium 20 adheres to the plated wires 10. Afterlamination, the external bias tension applied to plated wires 10 isremoved. Plated wires 10 immediately contract to attain a stress-freecondition in which no residual bias tension remains on the wires. Sincedielectric support medium 20 adheres to the plated wires but has atensile strength much less than that of plated wires 10, it similarlycontracts. Although the thermal coefficient of expansion of dielectricsupport medium 20 in this embodiment is ordinarily much larger than thatof plated wires 10, the ratio of the cross-sectional areas of dielectricsupport medium 20 and the grid of plated wires 10 is such that the totaltensile strength of the grid of plated wires 10 is greater than that ofdielectric support medium 20. Therefore plated wires 10 are held in arelatively stress-free condition over a desired temperature range.

In the next step of the method, selected portions of the thin metal topand bottom layers 13 and 14 are removed by photo-chemical techniqueswell known in the art. As a result, an array of parallel conductors 22is formed on the top and bottom surfaces of dielectric support medium20. FIG. 3 shows an array of conductors aligned orthogonal to plateswires 10. To form word strap conductors, circuit connection must be madebetween a conductor on the top surface and a conductor on the bottomsurface. Although several techniques are available for making thecircuit connections, one particularly successful method consists offorming holes through the dielectric material and plating the holes withan electrically conductive material to make circuit connections betweenthe conductors on the opposite surfaces. The plated-through hole 23illustrates the result of this technique.

FIG. 4 illustrates the final step of the method in which dielectricmaterial is selectively removed from the ends of the plated wires toallow electrical connec tions to be made to the plated wires. In apreferred embodiment of the present invention the dielectric material isremoved from the plated wire ends by heat stripping.

Heat sealable thermoplastic materials have been found to be suitable foruse as the dielectric support medium in the present invention. Examplesof such heat sealable thermoplastic materials include polyethylene,vinyl, polypropolene, nylon, polycarbonate, polyester, polystyrene,fluorocarbons and polyvinylchloride. In addition, adhesive thermosettingmaterials may also be used in the present invention as a dielectricsupport medium. Suitable adhesive thermosetting materials includephenolic and epoxy resins.

Because the tensile strength of the dielectric support medium is muchless than tensile strength of the plated wires, the dielectric supportmedium provides very little mechanical strength to the plated wirememory plane.

In one successful embodiment of the present invention, nickel-ironcoated beryllium-copper wires were used as the plated wire memoryelement. The wires had a diameter of 2% mils and a tensile strength ofabout 160 X 10 lbs./in. An external bias tension of approximately tograms was applied to the plated wires for alignment purposes. Thecenter-to-center spacing of the plated wires was about 0.0l0 inches. Theplated wires were positioned between two 0.002 inch thick sheets of type2 or type 3 polyethylene. The two sheets of polyethylene were bondedtogether at approximately l20C, thereby permanently embedding the platedwires. The finished thickness of the plated wire memory plane wasapproximately 4 mils.

In this embodiment, thin metal sheets as described in FIG. 1 were notutilized. Instead, a separate word strap envelope containing a pluralityof word strap conductors was positioned around the dielectric supportmedium having the plated wires embedded.

In some applications it is desirable to provide additional mechanicalstrength to the plated wire memory plane. One well known method ofproviding this additional mechanical strength is to utilize a reinforceddielectric material. In this case, however, the reinforced dielectricmaterial no longer has a tensile strength which is much less that thetensile strength of the plated wires. With another embodiment of thepresent invention, it is possible to utilize a reinforced dielectricsupport medium and still incorporate the plated wires as an integralpart of the dielectric support medium.

The fabrication of the reinforced unitized plated wire memory plane isquite similar to the method described previously. A plurality of platedwires are aligned in a parallel array. The plated wires have a firstthermal coefficient of expansion. An external bias tension is applied tothe plated wires. The external bias tension is less than the elasticlimit of the wire and the plating. For example, in 2% mil diameterberyllium-copper wire having a nickel-iron coating the maximum biastension is approximately grams. Although 50 grams is not the elasticlimit of the beryllium-copper wire, bias tensions greater than 50 gramspermanently damage the magnetic characteristics of the nickel-ironcoating. As previously described, the plated wires are positionedbetween a first and a second sheet of dielectric material. Thedielectric material has a second thermal coefficient of expansion whichis slightly greater than the first coefficient. The first and secondsheets are then bonded together to permanently embed the plated wires ina unitary body of dielectric material hereafter referred to as thedielectric support medium. The bonding occurs at a temperature greaterthan the desired operating temperature range. When bonding takes place,the dielectric support medium adheres to each of the plated wires. Sincethe tensile strength of the dielectric support medium is comparable tothat of the plated wires, a residual bias tension remains on the platedwires although the external bias tension has been removed. If thethermal coefficient of expansion of the dielectric material is slightlygreater than that of the plated wires, the dielectric material willapply a compressive force to the plated wires as the-plated wire memoryplane is cooled to temperatures within the desired operating temperaturerange. In the present invention the thermal coefficient of thedielectric support medium is so selected that the compressive forceapplied to the plated wire due to the difference between the first andsecond thermal coefficients effectively cancels the residual biastension on the plated wires over the desired operating temperaturerange.

Although a large variety of reinforced thermoplastic and thermosettingmaterials are available, one particularly successful dielectric supportmedium is formed by epoxy resin filled with glass fibers. The glassfibers increase the structural strength of the dielectric support mediumand also provide for an adjustable thermal coefficient of expansion. Theepoxy resin molded has a thermal coefficient of expansion which isapproximately 25.2 X 10 in/in/C while the glass fiber has a thermalcoefficient of 4.5 X in/in/C. The relative amounts of epoxy resin andglass fiber in the dielectric support medium determines the thermalcoefficient. The tensile strength of the epoxy resin glass fibercomposite is comparable to that of the plated wires, between about 50and 160 X 10 lbs/in depending upon the relative amounts of resin andfibers.

One successful embodiment of the reinforced unitized plated wire memoryplane utilized 2% mil diameter nickel-iron coated beryllium-copperwires. The plated wires have a thermal coefficient of expansion of about16.7 X 10' in/in/C. A 25 gram external bias tension was applied to theplated wires. The plated wires were positioned between two sheet-likelayers of partially cured epoxy resin which were filled with glassfibers. Each sheet was approximately three mils in thickness. Therelative amount of epoxy resin and glass fiber was such that the thermalcoefficient of the sheets was approximately 18 X 10 in/in/C. Thematerials were positioned between polished metal platens and bonded at apressure of approximately 200 pounds per square inch at a temperature ofapproximately 140C. After bonding, the thickness of the plated wirememory plane was about 6 to 7 mils.

Upon bonding, the dielectric support medium embeds and adheres to eachofthe plated wires thereby causing a residual bias tension to remain onthe plated wires even after the external biasrtension is removed. As thestructure cools to temperatures within the desired operating temperaturerange, the dielectric support medium applies a compressive force to thewires because the thermal coefficient of the dielectric support mediumis slightly greater than that of plated wires. In the above example, thedifference in thermal coefficients is such that the compressive forceapplied by the dielectric support medium cancels the residual biastension and yields a zero stress condition upon the wires atapproximately 25C. No significant performance change was noted over a50C temperature range (:1: 25C) and operation with a reduced output waspossible over a 150C temperature range 25C to 125C). Therefore, it canbe stated that over these operating temperature ranges the compressiveforce applied to the wires by the dielectric support medium effectivelycancels the residual bias tension. It can be seen that other operatingtemperature ranges can be obtained by adjusting the composition of theepoxy resin glass fiber composite and/or the external bias tensionapplied to the plated wire.

The word strap conductors may be formed by a method similar to thatdiscussed previously with respect to the unreinforced unitized platedwire memory plane. Another method of forming the word strap conductorswhich has proved effective has been to utilize two epoxy resin glassfiber sheets each having a copper layer attached to one surface. Afterthe dielectric support medium is formed by bonding the two sheetstogether, the copper layers, which are now on the outer surfaces of thedielectric support medium, are photochemically fabricated into an arrayof parallel word strap conductors. As described previously, thenecessary circuit connections between conductors on opposite surfaces ofthe memory plane are accomplished with plated through holes.

In order to make electrical connections to the ends of the plated wires,it is usually necessary to remove portions of the dielectric supportmedium. In the case of the reinforced epoxy resin glass fiber dielectricsupport medium, amixture of four parts sulphuric acid and one parthydrofluoric acid is particularly useful in selectively removing thedielectric material from the ends of the plated wires by etching.

In another embodiment of the present invention the bonding of the firstand second reinforced dielectric sheets together to permanently embedthe plated wires is accomplished at a temperature within the desiredoperating temperature range. For instance, bonding may occur at roomtemperature, which is a temperature within the desired operatingtemperature range. Examples of dielectric materials used in roomtemperature bonding include pressure-sensitive adhesive materials androom temperature curing wet epoxy resins. These dielectric materialsinclude a reinforcing material which contributes structural strength andadjusts the coefficient of thermal expansion of the dielectric supportmedium. The fabrication of the unitized plated wire memory plane isessentially identical to the process described previously for areinforced dielectric support medium. However, when bonding occurs at atemperature within the desired operating temperature range, the externalbias tension applied to the plated wires is the minimum amount oftension required for alignment of the wires and is less than the amountof tension which degrades the magnetic properties of the plated wires.In this manner the residual bias tension is minimized. Furthermore, thecomposition of the dielectric support medium is adjusted such that thethermal coefficient of expansion of the dielectric support medium isessentially identical to that of the plated wires. Therefore, over thedesired operating temperature range the only stress applied to theplated wires is that of the residual bias tension. By minimizing theexternal bias tension utilized, the residual bias tension on the platedwires is small and does not significantly degrade the performance of theplated wire memory plane. Fabrication of the word strap conductors isaccomplished by one of the methods described previously.

While this invention has been particularly shown and described withreference to the preferred embodiments thereof, it will beunderstood bythose skilled in the art that changes in form and details may be madewithout departing from the spirit or scope of the invention.

The embodiments of the invention in which an exclusive property or rightis claimed aredefined as follows:

1. A unitized plated wire memory plane in which plated wires areincorporated as an integral part of a dielectric support medium, thememory plane comprising:

a first grid of substantially parallel plated wires, each 7 wire havinga first thermal coefficient of expansion and having a residual biastension thereon,

a sheet-like dielectric support medium having a first and a secondsurface and a second thermal coeffcient of expansion different from thefirst coefficient, said dielectric support medium embedding and adheringto each of the plated wires of the first grid and applying a compressiveforce to the wires over a desired operating temperature range due to thedifference between the first and second coefficients such thatv thecompressive force effectively cancels the residual bias tension on thewires over the desired operating temperature range.

2. The unitized plated wire memory plane of claim 1 and furthercomprising:

a-second grid of substantially parallel conductors attached to the firstand second surfaces, the substantially parallel conductors beingorthogonal to the plated wires.

3. The unitized plated wire memory plane of claim 1 wherein the platedwires comprise nickel-iron coated beryllium-copper wires.

4. The unitized plated wire memory plane of claim 1 wherein thedielectric support medium comprises a reinforced thermosetting material.

5. The unitized plated wire memory plane of claim 4 wherein thereinforced thermosetting material comprises a composite of epoxy resinand glass fiber.

6. The unitized plated wire memory plane of claim 5 wherein the platedwire is comprised of nickel-iron coated beryllium-copper wires.

7. The unitized plated wire memory plane of claim 6 wherein the firstthermal coefficient of expansion is about 16.7 X in/in/C and the secondthermal coefficient of expansion is about 18 X 10 in/in/C.

8. A method of making a unitized plated wire memory plane in whichplated wires are incorporated as an integral part of a dielectricsupport medium, the method comprising:

positioning plated wires having a first thermal coefficient of expansionin a parallel array,

applying an external bias tension to the plated wires, the external biastension being less than the elastic limit of the plated wires,

positioning the plated wires between a first and a second sheet ofdielectric material, the dielectric material having a second thermalcoefficient of expansion different than the the first coefficient, andbonding the first and second sheets together at a temperature greaterthan a desired operating temperature range to permanently embed theplated wires in a unitary body of dielectric material formed by thefirst and second sheets, such that the unitary body of dielectricmaterial adheres to the plated wires and applies a compressive forceover the desired operating temperature range due to the differencebetween the first and the second coefficients which effectively cancelsa residual bias tension on the plated wires over the desired operatingtemperature range.

'9. The method of claim 8 wherein the plated wires comprise nickel-ironcoated beryllium-copper wires having a first thermal coefficient ofexpansion of about 16.7 X 10' in/in/C and the first and second sheetsare epoxy resin glass fiber composite material having a second thermalcoefficient of expansion of about 18 X 10 in/in/C, the step of bondingcomprising:

heating the first and second sheets and the plated wires to atemperature of about 140C, and applying a pressure of about 200 poundsper square inch to cause bonding together of the first and secondsheets. 10. The method of claim 9 wherein the external bias tension isabout 25 grams. I

11. The method of claim 8 and further comprising selectively removingthe dielectric material from the ends of the plated wires.

12. The method of claim 11 wherein the dielectric materialis an epoxyresin glass fiber composite and wherein selectively removing thedielectric material from the ends of the plated wires comprises etchingaway the epoxy resin glass fiber composite with a mixture of four partssulphuric acid and one part hydrofluoric acid.

13. The method of claim 8 and further comprising:

fabricating a grid of substantially parallel conductors adjacent to theunitary sheet and orthogonal to the plated wires.

14. The method of claim 13 wherein the step of fabricating comprises:

bonding a first and a second sheet of metal foil to 0pposite surfaces ofthe unitary body of dielectric material, and

selectively etching portions of the first and second sheets of metalfoil to form identical grids of substantially parallel conductors on theopposite surfaces of the unitary body, and

selectively making circuit connections between conductors on theopposite surfaces.

15. The method of claim 14 wherein selectively making circuitconnections comprises:

forming holes through the dielectric material, and I plating the holeswith an electrically conductive material to make circuit connectionsbetween conductors on the opposite surfaces.

16. A method of making a unitized plated wire memory plane in whichplated wires are incorporated as an integral part of a dielectricsupport medium, the method comprising:

positioning plated wires having a first thermalcoefficient of expansionin a parallel array,

applying an external bias tension to the plated wires sufficient toalign the plated wires, the external bias tension being insufficient todegrade the magnetic properties of the plated wires,

positioning the plated wires between a first and a second sheet ofdielectric material, the dielectric material having a second thermalcoefficient of expansion essentially identical to the first coefficient,and

bonding the first and second sheets together at a temperature within adesired operating temperature range to permanently embed the platedwires in a unitary body of dielectric material formed by the first andsecond sheets, such that the unitary body of dielectric materialmaintains the plated wires in an essentially stress free condition.

17. The method of claim 16 wherein the dielectric material is areinforced pressure sensitive adhesive material.

18. The method of claim 16 wherein the dielectric material is areinforced room temperature curing wet epoxy resin.

1. A unitized plated wire memory plane in which plated wires areincorporated as an integral part of a dielectric support medium, thememory plane comprising: a first grid of substantially parallel platedwires, each wire having a first thermal coefficient of expansion andhaving a residual bias tension thereon, a sheet-like dielectric supportmedium having a first and a second surface and a second thermalcoefficient of expansion different from the first coefficient, saiddielectric support medium embedding and adhering to each of the platedwires of the first grid and applying a compressive force to the wiresover a desired operating temperature range due to the difference betweenthe first and second coefficients such that the compressive forceeffectively cancels the residual bias tension on the wires over thedesired operating temperature range.
 2. The unitized plated wire memoryplane of claim 1 and further comprising: a second grid of substantiallyparallel conductors attached to the first and second surfaces, thesubstantially parallel conductors being orthogonal to the plated wires.3. The unitized plated wire memory plane of claim 1 wherein the platedwires comprise nickel-iron coated beryllium-copper wires.
 4. Theunitized plated wire memory plane of claim 1 wherein the dielectricsupport medium comprises a reinforced thermosetting material.
 5. Theunitized plated wire memory plane of claim 4 wherein the reinforcedthermosetting material comprises a composite of epoxy resin and glassfiber.
 6. The unitized plated wire memory plane of claim 5 wherein theplated wire is comprised of nickel-iron coated beryllium-copper wires.7. The unitized plated wire memory plane of claim 6 wherein the firstthermal coefficient of expansion is about 16.7 X 10 6 in/in/*C and thesecond thermal coefficient of expansion is about 18 X 10 6 in/in/*C. 8.A method of making a unitized plated wire memory plane in which platedwires are incorporated as an integral part of a dielectric supportmedium, the method comprising: positioning plated wires having a firstthermal coefficient of expansion in a parallel array, applying anexternal bias tension to the plated wires, the external bias tensionbeing less than the elastic limit of the plated wires, positioning theplated wires between a first and a second sheet of dielectric material,the dielectric material having a second thermal coefficient of expansiondifferent than the the first coefficient, and bonding the first andsecond sheets together at a temperature greater than a desired operatingtemperature range to permanently embed the plated wires in a unitarybody of dielectric material formed by the first and second sheets, suchthat the unitary body of dielectric material adheres to the plated wiresand applies a compressive force over the desired operating temperaturerange due to the difference between the first and the secondcoefficients which effectively cancels a residual bias tension on theplated wires over the desired operating temperature range.
 9. The methodof claim 8 wherein the plated wires comprise nickel-iron coatedberyllium-copper wires having a first thermal coefficient of expansionof about 16.7 X 10 6 in/in/*C and the first and second sheets are epoxyresin - gLass fiber composite material having a second thermalcoefficient of expansion of about 18 X 10 6 in/in/*C, the step ofbonding comprising: heating the first and second sheets and the platedwires to a temperature of about 140*C, and applying a pressure of about200 pounds per square inch to cause bonding together of the first andsecond sheets.
 10. The method of claim 9 wherein the external biastension is about 25 grams.
 11. The method of claim 8 and furthercomprising selectively removing the dielectric material from the ends ofthe plated wires.
 12. The method of claim 11 wherein the dielectricmaterial is an epoxy resin - glass fiber composite and whereinselectively removing the dielectric material from the ends of the platedwires comprises etching away the epoxy resin - glass fiber compositewith a mixture of four parts sulphuric acid and one part hydrofluoricacid.
 13. The method of claim 8 and further comprising: fabricating agrid of substantially parallel conductors adjacent to the unitary sheetand orthogonal to the plated wires.
 14. The method of claim 13 whereinthe step of fabricating comprises: bonding a first and a second sheet ofmetal foil to opposite surfaces of the unitary body of dielectricmaterial, and selectively etching portions of the first and secondsheets of metal foil to form identical grids of substantially parallelconductors on the opposite surfaces of the unitary body, and selectivelymaking circuit connections between conductors on the opposite surfaces.15. The method of claim 14 wherein selectively making circuitconnections comprises: forming holes through the dielectric material,and plating the holes with an electrically conductive material to makecircuit connections between conductors on the opposite surfaces.
 16. Amethod of making a unitized plated wire memory plane in which platedwires are incorporated as an integral part of a dielectric supportmedium, the method comprising: positioning plated wires having a firstthermal coefficient of expansion in a parallel array, applying anexternal bias tension to the plated wires sufficient to align the platedwires, the external bias tension being insufficient to degrade themagnetic properties of the plated wires, positioning the plated wiresbetween a first and a second sheet of dielectric material, thedielectric material having a second thermal coefficient of expansionessentially identical to the first coefficient, and bonding the firstand second sheets together at a temperature within a desired operatingtemperature range to permanently embed the plated wires in a unitarybody of dielectric material formed by the first and second sheets, suchthat the unitary body of dielectric material maintains the plated wiresin an essentially stress free condition.
 17. The method of claim 16wherein the dielectric material is a reinforced pressure sensitiveadhesive material.
 18. The method of claim 16 wherein the dielectricmaterial is a reinforced room temperature curing wet epoxy resin.